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Question
Find:
`a^3-1/a^3`, if `a -1/a = 4`.
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Solution
`a -1/a = 4`
`⇒ (a - 1/a)^3 = (4)^3`
`⇒ a^3 - 1/a^3 - 3a xx 1/a(a - 1/a) = 64`
Substitute the given value of `a - 1/a = 4` into the equation:
`⇒ a^3 - 1/a^3 + 3(4) = 64`
`⇒ a^3 - 1/a^3 - 12 = 64`
`⇒ a^3 - 1/a^3 = 64 + 12`
`⇒ a^3 - 1/a^3 = 76`
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